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SEISMIC LOADING IN STAADPRO NEED TO CHECK TOO MANUALY

 
This forum is locked: you cannot post, reply to, or edit topics.This topic is locked: you cannot edit posts or make replies.    www.sefindia.org Forum Index -> Past Discussions Year 2003
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anandrshah9
SEFI Member
SEFI Member


Joined: 26 Jan 2003
Posts: 13

PostPosted: Tue Dec 02, 2003 6:24 pm    Post subject: SEISMIC LOADING IN STAADPRO NEED TO CHECK TOO MANUALY Reply with quote

Hello friends and seniors,

I would like to contribute in the current discussion of seismic forces in
STAAD specifically with 2 notes.

1 we can apply E.Q. from two ways. One is calculation of E.Q. forces ( base
shear required as per IS 1893-2002 manually and applying each storey shear
at each floor from out side in program with rigid diaph. Action using slave
rigid master or slave fx fz master. Or we can specify necessary data in
programe to calculate total base shears by itself. But in later case I have
noticed that if we donít give time period px and pz along with necessary
data in edit file, then total base shear calculated by programe is not
matching with manual calculation as per code.
2 And the second thing, I have noticed is distribution of seismic forces
(storey shears ) at different level and in lateral load resisting elements
is different in both the cases , when we applied from outside with slave
rigid master or slave fx fz master on each rigid floor or we give necessary
data in programe to calculate and distribute itself. And even I have tried
to match it with manual approximate design like cantilever , portal or
substitute frame method, but that is also not matching.

These are the problem I have faced, and looking forward a  solutions.

Regards,

Anand Shah
(Dalal Mott Macdonald, Ahmedabad)





Quote:
From: bhumika.mehta@babtieindia.com
Reply-To: general@sefindia.org
To: anandrshah9@hotmail.com
Subject: Re: SEISMIC LOADING IN STAADPRO
Date: Mon Dec  1 10:54:24 2003

Hello sir,

To apply "Response Spectrum" in STAAD Pro, the command line in text file of
staad is

SPECTRUM "MODAL COMBINATION" "DIRECTION" "FACTOR" "RESPONSE" DAMP ______
SCALE _______
T  RESPONSE ;

The above command line specifies that the modal responses can be combined
using either CQC method or SRSS method. The spectrum can be applied in
global X, Y or Z direction with some factor (usually 1.0). The "Response"
may be acceleration or displacement. Damping ratio is 0.05 (damping 5%) for
concrete structures. The scale factor is the quantity by which spectral
accelerations (and spectral displacements) must be multiplied by before
they
are used in the calculations. The spectrum data is given as period vs.
acceleration.

Apply it after giving self-weight or dead load command.

For example,
As per IS 1893-2002 part 1, response spectrum ordinates in terms of T
(Natural period) and Acceleration for medium soil condition, structure
situated in zone 5 and for 5% damping is
0 0.54; 0.1 1.35
0.55 1.35; 1.0 0.73
1.5 0.49; 2.0 0.37
2.5 0.29; 3.0 0.24
3.5 0.21; 4.0 0.18

Command line for this spectrum is
LOAD 2 SEISMIC LOADING
SPECTRUM CQC X 1.0 ACC DAMP 0.05 SCALE 1.0
0 0.54; 0.1 1.35
0.55 1.35; 1.0 0.73
1.5 0.49; 2.0 0.37
2.5 0.29; 3.0 0.24
3.5 0.21; 4.0 0.18

In modeling mode

In "Commands" menu, go to loading,  primary load.
Define Load 2 as "seismic loading". Now load page will open. In that click
on spectrum and apply data as explained above.

Regards,
Bhumika





----------------------------------------------------------
From: dharikrishna@hotmail.com
Subject: SEISMIC LOADING IN STAADPRO
Date: 27/11/03
Time: 21:35:42
----------------------------------------------------------
HI FELLOW MEMBERS OF THE FORUM
HI I WISH TO KNOW IF ANY ONE SUGGESTS ME HOW TO  DEFINE THE SEISMIC
LOADING
IN STAAD PRO
I HAVE ANALYSED A 5 STORIED SHEAR FRAMED STRUCTURE USING STAADPRO
I GOT THE ANALYSIS RESULT FROM STAAD PRO
I WANT TO ANALYSE THE SAME FRAME USING RESPONSE SPECTRUM METHOD USING
STAADPRO
BUT I M UNABLE TO DEFINE THE SEISMIC LOAD CASE , SO PLEASE IF ANY ONE
COULD
SUGGEST ME IN THIS REGARD .. THEN I WILL BE GREAT FULL TO U
THANKING U ALL
FELLOW SEFI MEMBER

_________________________________________________________________




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_________________________________________________________________

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bhumika
SEFI Member
SEFI Member


Joined: 26 Jan 2003
Posts: 4

PostPosted: Thu Dec 04, 2003 8:53 am    Post subject: SEISMIC LOADING IN STAADPRO NEED TO CHECK TOO MANUALY Reply with quote

Hi Anand,

your second approach is very much close to the actual one that is acting on
the structure. but that depends upon how it distribute forces to the
columns.

One another way to define the static earthquake force is apply earthquake
force as a joint weight. For this you have to determine the distribution
factor for each column in two horizontal directions according to it's size.
and then this distribution factor is multiplied with the total weight of the
structure. Of course total weight of the structure is approximate.

I think this is the better way to assign seismic load than the Master slave
specification.

Regards,
Bhumika

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